The trigger
Nothing goes out at random. SGA watches a client's target companies and waits. A product ships. A partnership is announced. A new revenue leader starts. That is the moment a message has a reason to exist, and it is the only thing that starts one. No signal, no email.
What the agency owns
When a signal fires, SGA researches the company, decides which decision-maker the message actually belongs to, and writes to that one person about that one thing. The mail is sent from the client's own domain. Every sentence in it is the agency's responsibility, and the agency answers for it.
What comes back
Replies and booked meetings, handed to the client. The client does not run the research and does not write the emails. That is what done-for-you means here: the work sits on the agency's side of the line, and the conversations arrive on the client's.